Solid-phase extraction is a general process in which a solid phase (i.e., solid-phase extraction material) is used to separate a measurement component (i.e., a component to be measured) from impurities in a sample solution, depending on physical and chemical characteristics thereof. The solid-phase extraction is used in various analytical techniques (e.g., liquid chromatography, mass spectrometry) in order to purify a measurement component by removing impurities that prevent analysis.
Examples of a sample (or sample solution) that can be used for the analysis include urine, blood, and water. When the sample solution passes through a solid-phase extraction material, an affinity between a measurement component in the sample solution and the surface of the solid-phase extraction material may be high. In this case, the measurement component in the sample solution is selectively adsorbed. Accordingly, the measurement component can be purified or enriched.
A typical solid-phase extraction process includes three steps: an adsorption step of causing a measurement component in a sample solution to be adsorbed on a solid-phase extraction material; a cleaning step of removing impurities other than the measurement component adsorbed on the solid-phase extraction material; and an elution step of eluting the adsorbed measurement component from the solid-phase extraction material.
In the adsorption step, the measurement component is adsorbed on the solid-phase extraction material, and components preventing the analysis (i.e., impurities) flow out without being adsorbed. However, some impurities may be adsorbed on the solid-phase extraction material. Consequently, the adsorbed impurities should be removed in the cleaning step.
In the elution step, an eluent is used to separate the purified measurement component from the solid-phase extraction material. In addition, the post-separation eluate containing the measurement component is sent to an analyzer, where a signal intensity of the measurement component is measured.
As described above, the solid-phase extraction is carried out in the order of the adsorption step, the cleaning step, and the elution step. Accordingly, the impurities are removed and the measurement component is purified.
Further, as a solid-phase extraction kit, widely used are, for example, a syringe-type solid-phase extraction cartridge in which a solid-phase extraction material is interposed between filters in a syringe, and a 96-well solid-phase extraction cartridge in which a solid-phase extraction material is interposed between filters in a container for a 96-well microplate.
Examples of a device that automatically performs the above adsorption, cleaning, and elution steps include: a device disclosed in Patent Literature 1 that uses a pressurizing mechanism to apply pressure on a sample solution, thereby making the sample solution flow through a solid-phase extraction material; a solid-phase extraction device disclosed in Patent Literature 2 that uses a pressure-reducing mechanism to make a sample solution flow through a solid-phase extraction material; and a solid-phase extraction device disclosed in Patent Literature 3.
Further, Patent Literature 4 discloses solid-phase extraction cartridges used for the analyzers disclosed in, for example, Patent Literatures 1 and 2.